hacked by the ghost louay on wp-admin

I have iThemes Security on one of my clients sites and it seems there’s been some hacking going on. If I go to her wp-admin, I get the message “hacked by the ghost louay” at /not_found instead of the standard ‘Not available.’ error message I should receive. I do have a cloaked URL using iThemes, so I do get into my wp-admin just fine. However, I’d like to get rid of this redirect to the ‘hacked’ message.